Alsace is the fifth-smallest of the 27 regions of France in land area (8,280 km²), and the smallest in metropolitan France. It is also the seventh-most densely populated region in France and third most densely populated region in metropolitan France, with ca. 220 inhabitants per km² (total population in 2006: 1,815,488; 1 January 2008 estimate: 1,836,000). Alsace is located on France's eastern border and on the west bank of the upper Rhine adjacent to Germany and Switzerland. The political, economic and cultural capital as well as largest city of Alsace is Strasbourg. Because that city is the seat of dozens of international organizations and bodies, Alsace is politically one of the most important regions in the European Union. The name "Alsace" can be traced to the Old High German Ali-saz or Elisaz, meaning "foreign domain". An alternative explanation is from a Germanic Ell-sass, meaning "seated on the Ill",a river in Alsace. The region was part of the Holy Roman Empire, and then was gradually annexed by France in the 17th century, under Louis XIII and Louis XIV, and formalized as one of the provinces of France. The calvinist manufacturing republic of Mulhouse, known as Stadtrepublik Mülhausen, become a part of Alsace after a vote by its citizens on 4 January 1798. Alsace is frequently mentioned with Lorraine, because German possession of parts of these two régions (as the imperial province Alsace-Lorraine, 1871–1918) was contested in the 19th and 20th centuries; France and Germany exchanged control of Alsace four times in 75 years. The historical language of Alsace is Alsatian, similar to German dialects spoken across the Rhine, but today practically all Alsatians speak French, the official language of France. 43% of the adult population, and 3% of children (3 to 17 years old), stated in 2012 that they speak Alsatian. The place names used in this article are in French. See this list for the German place names.